Welcome to the August 2019 issue of Thorne’s Research Extracts – designed to keep busy practitioners and savvy consumers up-to-date on the latest research on diet, nutrients, botanicals, the microbiome, the environment, and lifestyle approaches to good health. Our medical team, which includes NDs, MDs, PhDs, RDs, and an MS, LAc, and CCN, has summarized the essence of several of the most interesting studies.

Research summaries in this issue include: (1) coffee and colon cancer, (2) dairy products and type 2 diabetes, (3) sleep and metabolic syndrome, and (4) sleep and breast cancer.

Also in this issue are links to two audio podcasts: (1) carotenoids and brain/eye health and (2) microbiome testing.

Dose-response meta-analysis of coffee consumption and risk of colorectal cancer

Colorectal cancer is the third-most common cancer in men, and the second-most common cancer in women. Coffee is one of the most commonly consumed drinks in the world, with 10 million tons consumed yearly. 

Several meta-analyses have been published on coffee consumption and its relationship to colorectal cancer risk, with some variability in result.

This study sought to study the relationship between coffee intake and colorectal adenoma risk and to quantify the dose-relationship between coffee intake and the risk of colorectal cancer.

The researchers conducted a meta-analysis of cohort and case-control studies to poll data and sum the existing research. Eight studies, with a total of 7,090 subjects, published between 1990 and 2015 (six case-control studies and two cohort studies) were identified. Daily coffee intake from 0-7 cups was studied, with wide variability among the studies. 

High coffee intake compared with the lowest intake was associated with a reduced risk of colorectal cancer. The meta-analysis demonstrates possible evidence that increased coffee intake is related to a reduced risk of colon cancer.

A dose-response meta-analysis of coffee intake performed on five of the studies showed a linear and inverse relationship between coffee drinking and colorectal cancer risk. The estimated odds ratio for increasing coffee consumption by one cup per day was 0.91.

Contributed by Amanda Frick, ND, LAc

Reference

  • Wang Y, Chen J, Zhao R, et. al. Dose-response meta-analysis of coffee consumption and risk of colorectal adenoma. Eur J Clin Nutr 2019; doi: 10.1038/s41430-019-0467-0

Dairy products and type 2 DM

A handful of alternative practitioners have been arguing for years that milk consumption is not only unnecessary but actually harmful. The most vehement claims are based on the argument that the ingestion of dairy products results in an increased release of both insulin and insulin growth factor, thus exacerbating insulin resistance. A review of the literature, however, suggests the contrary.

A review recently published in Advances in Nutrition analyzed the evidence of dairy product consumption and the risk of type 2 diabetes (T2D). Eight experts presented a summary of the evidence in his/her area of expertise at a workshop at Wageningen University in The Netherlands, each of which was challenged in extensive discussion.

The eight scientists were selected based on their previous publications on dairy products and diabetes-related topics. The review discusses the experts’ summaries of large prospective cohort studies and limited randomized controlled trials.

Areas addressed in the presentations included the intake of total dairy, liquid milk, fermented dairy, butter, cream, ice cream, and dairy fat content.

The conclusions from the workshop were that available evidence suggests that total dairy consumption has a neutral or moderately beneficial effect on T2D risk and that yogurt is most strongly associated with a lower risk of T2D. Low-fat dairy appeared to be more often associated with a lower T2D risk than high-fat dairy, but the effect was small and considered borderline.

Although numerous gaps in the existing knowledge were identified and key research questions to be addressed were highlighted to better understand the impact of dairy consumption on T2D risk, the scales are tipped in favor of dairy products.  

Contributed by Danielle Paciera, LDN, RD, CCN

Reference

  • Guo J, Givens D, Astrup A, et al. The impact of dairy products in the development of type 2 diabetes: Where does the evidence stand in 2019? Adv Nutr 2019 May 24. pii: nmz050. doi: 10.1093/advances/nmz050.

Review of sleep’s effect on metabolic syndrome

A review of studies looking at the impact of sleep on metabolic syndrome found a two-sided effect, which correlated too little slow-wave sleep (stage 3) or too much REM sleep with an increased risk for metabolic syndrome.

The authors suggest several overlapping and interacting mechanisms could explain these effects, including light-dark cycles, circadian rhythms, and sleep habits. Together, these combine to impact recovery, restful sleep, insulin-resistance, and feeding habits that can lead to metabolic disorder.

Levels of growth hormone (GH) and GH releasing hormone (GHRH) increase with slow-wave sleep, which occurs more frequently during the first half of the night (darkness), especially before midnight. 

Slow-wave sleep corresponds to the deepest, most restful sleep when body systems are most suppressed. GH, especially, is associated with adipose metabolism, bone growth, leptin and ghrelin hormones (satiety and hunger, respectively) that can influence feeding habits, and overall recovery as a result of sleep.

Studies have found that going to bed later in the dark phase of the day results in fewer stage 3 cycles and lower GH levels, thus negatively impacting these other pathways.  

In the second half of the night (after midnight), REM sleep frequency and cortisol levels increase.  Cortisol, the fight-or-flight hormone, activates body systems needed for action. During REM sleep the body’s functions are highest, with increases in heart rate, blood pressure, and other stress-related body systems occurring.

Studies have found that waking later into the light phase of the day results in more REM cycles, higher levels of cortisol during sleep, an increased incidence of negative dreaming, and increased chances of waking during a REM cycle, which can result in feeling less rested throughout the day. Elevated cortisol is also associated with weight gain, particularly abdominal fat.

Correlations have also been found between sleep insufficiency and increased insulin resistance, pro-inflammatory cytokines, β amyloid plaque and tau tangle formation, and decreased astrocyte activity/ability to clear plaques and tangles.   

The authors recommend getting to bed by 10:00 pm and waking at 4:30 am in the summer, 9:00 pm to 4:30 am for the longer nights of winter. They also suggest avoiding stimulants like caffeine and intense exercise before sleep.

Contributed by Sheena Smith, MS (Biol)

References

  • Smiley A, Wolter S, Nissan D. Mechanisms of association of sleep and metabolic syndrome. J Med Clin Res & Rev 2019;3(3):1-9.
  • Full text available here

New data connects sleep patterns to risk for breast cancer

Connections between sleep and breast cancer risk have long been established in the literature. For example, night-shift workers are known to be at higher risk for breast cancer,1 which is thought to be tied to a loss of production of the hormone melatonin. In addition to its regulatory role in sleep, melatonin regulates aspects of immune function, which could account for this risk.2

A new analysis now links different sleep traits to breast cancer risk. The current study, a multivariate regression analysis, was conducted using 400,000 respondents to a survey of a large data bank

 Those accepted into the trial, women ages 40 to 70, completed a questionnaire about various aspects of health and lifestyle – with a focus on sleep habits, including sleep length and preference for going to bed or waking early or late. Participants were then cross-referenced to diagnostic codes for breast cancer.

A sub-group of 50,000 participants also had available genetic data searched for 341 single nucleotide polymorphisms (SNPs) associated with sleep preferences, 91 SNPs associated with sleep duration, and 57 SNPs associated with insomnia. The study found a reduced risk of breast cancer in early risers and an increased risk in women who slept more than 7-8 hours per night.

In addition, the study confirmed previously established associations, such as finding a higher risk for breast cancer in women who are older, who have a higher BMI, have a history of smoking, or are more sedentary.

Contributed by Jacqueline Jacques, ND

References

  • Richmond R, Anderson E, Dashti H, et al. Investigating causal relations between sleep traits and risk of breast cancer in women: mendelian randomisation study. BMJ 2019 Jun 26;365:l2327. doi: 10.1136/bmj.l2327
  • Hansen J. Increased breast cancer risk among women who work predominantly at night. Epidemiology 2001 Jan 1;12(1):74-77.
  • Liu S, Madu C, Lu Y. The role of melatonin in cancer development. Oncomedicine 2018 May;3(1):37-47.

Podcast episode: The importance of macular carotenoids in eye and brain health

The carotenoids lutein and zeaxanthin are important elements of visual and brain health. Dr. Alan Miller hosts this podcast interview with Dr. Dashani Rai, an expert on these essential macular carotenoids.

Listen here

Podcast episode: Microbiome testing from Onegevity Health

Dr. Joel Dudley and Dr. Chris Mason are experts in the microbiome and in how to utilize the trillions of data points from microbiome testing using machine learning (artificial intelligence) to analyze this data for patterns that can inform about the health of the individual, as well as to provide actionable insights that can maximize health. Dr. Alan Miller interviews these brilliant and fun scientists. 

Listen here

Editor’s note:

It looks like we have two beverages that have previously been demonized that we can now feel better about – coffee and milk – so if you like lattes, you’re really in luck. It also looks like we have two reasons to consider going to bed earlier and getting up earlier – decreased breast cancer risk (if you’re a woman) and decreased risk for imbalances associated with metabolic syndrome. G’night!